Colostrum for the Immune System: What Clinical Trials Actually Found
Bovine colostrum is often marketed as an "immune booster," but the research behind that phrase is narrower and more interesting than the label suggests. Most of the human trials looked at one question: does colostrum change how often healthy, physically active adults report upper respiratory symptoms, especially during hard training? Below we go through what those trials measured, what they found, how large the effects were, and where the evidence is still thin.
Key takeaways
- Most controlled human trials used 10–60 g of colostrum per day for 8–12 weeks, mostly in athletes or active men.
- A 2016 meta-analysis of randomised trials found fewer self-reported upper respiratory symptom days and episodes with colostrum. It pooled only a handful of small studies.
- Some studies suggest colostrum may help maintain salivary IgA and limit exercise-related gut permeability. These are markers, not clinical outcomes.
- Evidence in older adults, children and the general population is limited and often uncontrolled.
- Colostrum is a dietary supplement. It is not shown to treat, cure or prevent any disease.
What is in colostrum that could plausibly affect immunity?
Colostrum is the first milk a cow produces after calving. Its composition is very different from ordinary milk. For a fuller primer, see What Is Colostrum?. The components most often discussed in immune research are:
- Immunoglobulins (mainly IgG): First-milking bovine colostrum can hold 50 g or more of IgG per litre, while mature milk holds under 1 g/L. Commercial dried powders are usually standardised to about 15–30% IgG by weight, so a 20 g serving provides roughly 3–6 g of IgG.
- Lactoferrin and lactoperoxidase: Iron-binding and antimicrobial proteins found in higher amounts in early milk.
- Growth factors: Including IGF-1 and TGF-β. These are studied mainly for gut-lining effects.
- Oligosaccharides and cytokines: Present in small amounts. Their role in humans after oral intake is poorly understood.
A key caveat is that bovine IgG is not absorbed into the human bloodstream in any meaningful amount. Researchers think any effect probably happens locally, in the mouth, throat and gut, rather than by "adding antibodies" to your blood.
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The respiratory symptom trials
Most of the human evidence comes from trials that tracked self-reported upper respiratory tract symptoms (URTS). That usually means daily logs of sore throat, runny nose and similar complaints, sometimes scored with a validated questionnaire. Here are the best-known studies.
Brinkworth & Buckley (2003)
This Australian randomised, double-blind trial gave adult men either 60 g/day of a concentrated colostrum protein or a whey protein placebo for 8 weeks. Fewer men in the colostrum group reported URTS during the study. The authors suggested a possible protective effect. The study had real limitations: symptoms were self-reported, there was no laboratory confirmation of infection, and the dose was high.
Crooks et al. (2006)
This New Zealand study gave distance runners 26 g/day of colostrum or a placebo for 12 weeks and measured salivary IgA, an antibody on mucosal surfaces that tends to drop after heavy training. Salivary IgA rose in the colostrum group compared with placebo. The difference in respiratory symptoms was less clear. The study shows a change in a marker, not proof of fewer illnesses.
Jones et al. (2014)
This UK randomised, double-blind trial gave 53 physically active men 20 g/day of colostrum or an isoenergetic placebo for 12 weeks during winter. The colostrum group had fewer upper respiratory illness days and fewer episodes. The researchers also saw differences in some salivary markers. This is one of the better-designed trials, but it was still small and included only men.
The 2016 meta-analysis
Jones and colleagues later pooled five randomised controlled trials of colostrum and upper respiratory symptoms in people who exercise. Colostrum was linked to a lower rate of symptom days (roughly 40–45% fewer) and symptom episodes (roughly 35–40% fewer) than placebo. Those numbers sound impressive, but the pooled sample was small, most participants were young men, and nearly all outcomes were self-reported. The authors themselves called for larger, better-controlled studies.
Trials at a glance
| Study | Population | Daily dose | Duration | Main finding | Main limitation |
|---|---|---|---|---|---|
| Brinkworth & Buckley, 2003 | Adult men | 60 g colostrum protein | 8 weeks | Fewer reporting URTS vs whey | Self-report; high dose |
| Crooks et al., 2006 | Distance runners | 26 g | 12 weeks | Salivary IgA increased vs placebo | Marker outcome; small sample |
| Jones et al., 2014 | 53 active men | 20 g | 12 weeks | Fewer illness days and episodes | Men only; self-report |
| Davison et al., 2016 | Healthy volunteers | 20 g | 14 days | Smaller exercise-induced rise in gut permeability | Short; lab marker only |
| Jones et al., 2016 (meta-analysis) | 5 RCTs, mostly active men | ~10–60 g | 4–12 weeks | Fewer URTS days and episodes | Few, small trials |
The gut barrier angle
A separate line of research looks at the gut. Hard exercise, especially in heat, can temporarily make the intestinal lining more permeable. In a 2016 study by Davison, Playford and colleagues, 20 g/day of colostrum for 14 days, alone or with zinc carnosine, reduced the rise in a sugar-based permeability test after strenuous exercise, compared with placebo. The gut lining is a major part of the body's barrier defences, so this finding is relevant. It remains a short-term laboratory marker in a small group, and it is not evidence of fewer infections.
Where the evidence is weak
- Narrow populations: Most participants were young, fit men. We cannot assume the results apply to women, older adults, children or people with medical conditions.
- Self-reported outcomes: Few trials confirmed infections with laboratory tests. Symptom diaries are useful but subjective.
- Small samples: Many trials enrolled fewer than 60 people, so effect estimates are imprecise.
- Uncontrolled paediatric data: A 2016 study by Saad and colleagues reported fewer respiratory and diarrhoeal episodes in children after colostrum. It had no placebo group, so it cannot separate the effect of colostrum from natural improvement over time.
- Product variation: Trials used different products, IgG levels and processing methods. A result from one product may not carry over to another.
- Hyperimmune products are different: Some older studies used colostrum from cows immunised against specific pathogens. Those results do not apply to standard retail colostrum.
Translating the research into practical choices
If you want to try colostrum, it makes sense to follow the trials. The most-studied range is about 10–20 g/day, taken consistently for at least 8 weeks. Some trials split the dose into two servings. Higher doses (up to 60 g) have been used, but they cost more and are less studied for long-term use.
A 20 g serving of typical colostrum powder has roughly 70–80 kcal and about 12–16 g of protein, depending on the fat and lactose content. Capsules usually contain only 0.5–1 g each, so getting close to trial doses with capsules can mean taking many a day. Our guide to how to choose a colostrum supplement explains how to read IgG claims and processing details.
Colostrum contains milk proteins and lactose, so it is not suitable for people with a cow's milk allergy. People with lactose intolerance may also notice symptoms. See dosage and safety for more detail, and speak with a clinician if you are pregnant, immunocompromised or taking medication.
FAQ
Does colostrum stop you from catching colds?
No trial shows that. Several small randomised trials in active adults found fewer self-reported upper respiratory symptom days with colostrum than with placebo. That is a modest, population-level finding, mostly in young men who train hard. It does not mean colostrum prevents colds, and it should not replace vaccination, sleep, hand hygiene or medical care.
How much colostrum did the studies use?
Most trials used 10–26 g of powder per day, and one used 60 g of a concentrated protein. Typical durations were 8–12 weeks. Short-term use or very small doses, such as one or two 500 mg capsules, have not been well studied for immune outcomes. The benefits reported in trials came from much larger, sustained intakes.
Does a higher IgG percentage mean better results?
Not necessarily. IgG is the most commonly measured marker of colostrum quality, and many products state 15–30%. No trial has directly compared IgG levels against clinical outcomes. Other components, such as lactoferrin and growth factors, may also matter. A verified IgG figure is still a useful sign of quality and consistency.
Is the evidence good enough to recommend colostrum?
The evidence is promising but preliminary. It is strongest for self-reported respiratory symptoms in physically active adults and weakest for children, older adults and the general public. It is reasonable to try colostrum as a supplement with realistic expectations. Stronger claims will need larger, more diverse trials with laboratory-confirmed outcomes.
Sources
- Brinkworth GD, Buckley JD. Concentrated bovine colostrum protein supplementation reduces the incidence of self-reported symptoms of upper respiratory tract infection in adult males. European Journal of Nutrition. 2003;42(4):228–232.
- Crooks CV, Wall CR, Cross ML, Rutherfurd-Markwick KJ. The effect of bovine colostrum supplementation on salivary IgA in distance runners. International Journal of Sport Nutrition and Exercise Metabolism. 2006;16(1):47–64.
- Jones AW, Cameron SJ, Thatcher R, Beecroft MS, Mur LA, Davison G. Effects of bovine colostrum supplementation on upper respiratory illness in active males. Brain, Behavior, and Immunity. 2014;39:194–203.
- Jones AW, March DS, Curtis F, Bridle C. Bovine colostrum supplementation and upper respiratory symptoms during exercise training: a systematic review and meta-analysis of randomised controlled trials. BMC Sports Science, Medicine and Rehabilitation. 2016;8:21.
- Playford RJ, Weiser MJ. Bovine colostrum: its constituents and uses. Nutrients. 2021;13(1):265.
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